Question

If you are given a kinetic energy of 18J and a mass of 0.0004 kg, what is the velocity?

Question 3 options:

212.13 m/s


90,000 m/s


0.003 m/s


300 m/s

Answer 1

To find the velocity given the kinetic energy (KE) and mass (m), we can use the formula for kinetic energy:

\[
KE = \frac{1}{2} m v^2
\]

Where:
- \( KE \) is the kinetic energy (18 J)
- \( m \) is the mass (0.0004 kg)
- \( v \) is the velocity

We can rearrange the formula to solve for velocity \( v \):

\[
v = \sqrt{\frac{2 \cdot KE}{m}}
\]

Now, substitute the values into the equation:

1. Calculate \( 2 \cdot KE \):

\[
2 \cdot 18 \, \text{J} = 36 \, \text{J}
\]

2. Divide by the mass:

\[
\frac{36 \, \text{J}}{0.0004 \, \text{kg}} = 90000 \, \text{m}^2/\text{s}^2
\]

3. Take the square root:

\[
v = \sqrt{90000} \approx 300 \, \text{m/s}
\]

Thus, the velocity is approximately **300 m/s**.

The correct answer from the options given is **300 m/s**.